1. Field of the Invention
The present invention relates to an electronic watch and, more particularly, to an electronic watch which can be small-sized even with a calendar indicating function.
2. Related Art
FIG. 17 is a top plan view showing one example of the electronic watch of the prior art. This electronic watch 900 having an auto-calendar function, which is provided in addition to a time indicating stepping motor 901 with a stepping motor 902 for a calendar indicating mechanism so that it can be freed from the trouble of correcting the date at the end of a month by driving the calendar portion independently of the time indicating portion. The stepping motor 902 is composed of a coil 921, a stator 922 and a rotor 923, which is provided with a reduction gear mechanism 904 for transmitting a rotating torque to a date ring 903. The rotor 923 is equipped with a pinion 924 for transmitting a rotating torque to the reduction gear mechanism (or a reduction gear train). This reduction gear mechanism 904 is composed of a first intermediate date ring 941 and a second intermediate date gear 942.
The calendar indication mechanism is composed of the date ring 903 having an inner circumference toothed at 932, and a date gear 931 engaging with the second intermediate date gear 942 for transmitting the rotating torque to the date ring 903. This date ring 903 is rotatably arranged on the (not-shown) calendar back plate.
The stepping motor 902 is electrically connected with a circuit block attached to the back of a base plate 905, so that it is rotated with drive pulses coming from an electronic circuit. The rotations of the stepping motor 902 are transmitted to the date gear 931 through the pinion 924 of the rotor 923, the first intermediate date ring 941 and the second intermediate date ring 942.
The date gear 931 engages with the teeth 932 so that the date ring 903 is rotated by the rotations of the date gear 931.
Since the torque to be generated by the stepping motor 902 is seriously low, however, the multistage reduction gear mechanism 904 is necessary for rotating the date ring 903. This has raised a problem that it is difficult to reduce the size of the electronic watch 900 which has multiple functions to indicate a variety of data in addition to the time information such as the auto calendar function.
Since the stepping motor 902 belongs to an electromagnetic conversion mechanism, on the other hand, it may exert an influence on the time indicating stepping motor 901. This makes it necessary to retain a distance between the two stepping motors 901 and 902. This necessity has made it impossible to reduce the size of the multi-function electronic watch 900.
Thus, the invention has been conceived in view of the foregoing description and has an object to provide an electronic watch which can be small-sized even with an additional function such as the calendar mechanism.
In order to achieve the above-specified object, according to the invention, there is provided an electronic watch wherein a piezoelectric actuator to be displaced by applying a voltage thereto is arranged in the vicinity of a portion of a second indication member for indicating data other than the time and is brought into press contact with the second indication member to drive the same directly.
When an alternating voltage or a pulsating voltage is applied to the piezoelectric element composing the piezoelectric actuator, the piezoelectric element is elongated and contracted by the piezoelectric effect so that a displacement corresponding to the applied voltage is established in the piezoelectric actuator. With the construction in which the piezoelectric actuator is brought into press contact with the second indication member, the displacement of the piezoelectric actuator causes a driving force of the second indication member through a friction. As the second indication member, there can be enumerated a date ring for indicating the date information, a chronograph and a moon face, for example. The piezoelectric actuator generates a higher force per unit volume than that of the stepping motor so that it can be made smaller in volume than the stepping motor and can be confined in the vicinity of a portion of the second indication member. Moreover, the high force makes the reduction gear mechanism unnecessary so that the electronic watch can be small-sized. Without the electromagnetic conversion mechanism, on the other hand, the piezoelectric actuator is not adversely affected by the time indicating stepping motor. Since the piezoelectric actuator need not be arranged apart from the time indicating stepping motor, therefore, it is possible to obtain an effect that the degree of freedom for designing the electronic watch is drastically enhanced. Here, similar operations and effects can be achieved in the invention, as will be described in the following.
According to the invention, on the other hand, there is provided an electronic watch wherein a second indication member for indicating data other than the time is disposed to confront a base plate, and wherein a piezoelectric actuator for establishing a displacement when a voltage is applied thereto is arranged between the base plate and the second indication member and is brought into press contact with the second indication member to drive the same directly.
The piezoelectric actuator is arranged between the second indication member such as the date ring and the base plate and is directly driven with the laminated structure in which it is is brought into press contact with the second indication member. As a result, the planar space can be drastically reduced while eliminating the reduction gear train, so that the multi-function electronic watch can be remarkably small-sized.
According to the invention, on the other hand, there is provided an electronic watch wherein a second indication member for indicating data other than the time is disposed to confront a base plate, wherein the second indication member is provided with a beam portion on its face confronting the base plate, and wherein a piezoelectric actuator for establishing a displacement by applying an electric signal to a piezoelectric element is brought into press contact with the side face of the beam portion thereby to drive the second indication member directly.
The construction is made such that the second indication member such as the date ring is provided with the beam portion on its face confronting the base plate and such that the piezoelectric actuator is brought into press contact with the side face of the beam portion. As a result, the mechanism for forcing the piezoelectric actuator to contact with the side face of the beam portion can be planarly arranged so that the electronic watch can be small-sized and thinned. With this construction, on the other hand, the contacting state of the piezoelectric actuator and the second indication member can be stabilized to provide another effect that the drive of the second indication member can be excellently stabilized. The method of applying the piezoelectric actuator to the beam portion maybe exemplified by urging the piezoelectric actuator directly or by pushing the piezoelectric actuator from the face opposed to the contacting face. Another effect is that a high degree of freedom for the design can be achieved to reduce the size of the electronic watch effectively.
On the other hand, an electronic watch according to the invention is characterized in that the piezoelectric actuator is a rectangular piezoelectric oscillator including: a first rectangular piezoelectric element having on its surface four divided electrodes, two individuals of which are electrically shorted to construct two sets of electrode groups; and a second rectangular piezoelectric element having an electrode extending substantially all over the surface, and in that the rectangular piezoelectric oscillator is caused to generate bending oscillations and longitudinal oscillations harmonically by applying a predetermined alternating voltage to the individual electrodes of the rectangular piezoelectric element.
The rectangular piezoelectric oscillator is used as the piezoelectric actuator so that the second indication member such as the date ring is directly driven in the frictional manner by the oscillatory waves. By using the resonant phenomenon between the bending oscillations and the longitudinal oscillations, the elliptical motions are obtained in the surface of the rectangular oscillator so that a slippage between the forced contacting faces of the piezoelectric actuator and the second indication member is reduced to provide a high efficiency.
As set forth in the inventions above, on the other hand, an electronic watch according to the invention is characterized in that the piezoelectric actuator is a piezoelectric oscillator including: a first rectangular piezoelectric element having on its surface four electrodes which are equally divided in a cross shape and two orthogonal ones of which are electrically shorted to construct two sets of electrode groups; and a second rectangular piezoelectric element having an electrode extending substantially all over the surface, and in that the rectangular piezoelectric oscillator is caused to generate bending oscillations and longitudinal oscillations harmonically by applying a predetermined alternating voltage to the individual electrodes of the rectangular piezoelectric element.
In the rectangular piezoelectric oscillator to be used as the piezoelectric actuator, there is used the first rectangular piezoelectric element having on its surface the four electrodes which are equally divided in the cross shape and the two orthogonal ones of which are electrically shorted to construct the two sets of electrode groups. According to this construction, the strong bending oscillations can be established, and a higher force can be generated in addition to the effect of the invention according to the inventions above. As a result, the piezoelectric actuator itself can be small-sized to reduce the size and thickness of the electronic watch having the multiple functions.
As set forth in the inventions above, on the other hand, an electronic watch according to the invention is characterized in that the piezoelectric actuator is a laminated piezoelectric oscillator prepared by laminating and sintering a plurality of rectangular piezoelectric elements including the first rectangular piezoelectric element and,the second rectangular piezoelectric element.
By using the laminated piezoelectric oscillator which is prepared by laminating and sintering the rectangular piezoelectric elements, the generated force of the piezoelectric actuator is increased according to the number of layers. A higher output can be made in a smaller size so that the piezoelectric actuator itself can be drastically small-sized to provide an advantage in the size reduction of the electronic watch.
As set forth in the inventions above, on the other hand, an electronic watch according to the invention is characterized in that the piezoelectric actuator includes a protrusion is brought into press contact with the second indication member to drive the same directly.
Since the second indication member is is brought into press contact with the protrusion formed on the piezoelectric a actuator, there is achieved an effect to extract only the displacement component which is effective for driving the second indication member directly by the friction from the displacement of the piezoelectric actuator. Thus, it is possible to realize the stable drive of the second indication member of a high performance.
As set forth in the inventions above, on the other hand, an electronic watch according to the invention is characterized by further comprising: a base plate prepared by combining a first base plate and a second base plate having a fitting portion, and in that the piezoelectric actuator and the second indication member are mounted on the second base plate.
The base plate is given the divided structure, and one base plate is provided with the piezoelectric actuator and the second indication member other than the time indication. When the electronic watch without the second indication member such as the date function is to be manufactured, therefore, it can be constructed exclusively of the first base plate without the second base plate having the date ring and the piezoelectric actuator for driving the date ring directly. On the contrary, the electronic watch having an additional function such as the date function of multiple functions can be manufactured not by changing the first base plate having the time indication portion but merely by fitting the second base plate for the date function in the first base plate. By thus using the second base plate having the second indication member and the piezoelectric actuator acting as the drive source for the former, the first base plate acting as the time indication portion common among the electronic watches can be shared among all the kinds of electronic watches so that various electronic watches of multiple functions can be provided at reasonable prices.
As set forth in the inventions above, on the other hand, an electronic watch according to the invention is characterized by further comprising: second indication member movement amount detecting means for detecting the movement of the second indication member; and a control circuit for controlling the piezoelectric actuator on the basis of a signal which is detected by the second indication member movement amount detecting means.
The amount of the movement of the second indication member is detected so that the control circuit controls the driven state of the piezoelectric actuator on the basis of that amount of the movement. In the case of the date ring in which the second indication member displays the date information, for example, it is detected by the second indication member movement amount detecting means whether or not the date ring is rotated for one day. The piezoelectric actuator is driven by the control circuit till the amount of the movement for one day is reached. When the predetermined amount of the movement is exceeded, a backward run is effected to stop the drive of the piezoelectric actuator at a predetermined position.
As set forth in the inventions above, on the other hand, an electronic watch according to the invention is characterized by further comprising: a rotary member engaging with and interlocked by the second indication member, and in that the second indication member movement amount detecting means detects the amount of the movement of the second indication member by detecting the rotating state of the rotary member.
The amount of the movement of the second indication member is detected by detecting the rotating state of the rotary member engaging with the second indication member. As a result, the rotation angle of the rotary member may be sufficient for detecting the amount of the movement of the second indication member more accurately so that the accurate control of the additional function can be made to provide an electronic watch of a high performance.